Managing heat dissipation of electronic components such as those in portable systems continues to be a challenge for engineers and designers. Portable computers pose a significant thermal management problem because of the need to increase their computational capabilities as well as their portability. Portable computers such as laptops or hand-held computers have higher power densities than desktop computers that use the same processor chips. Forced convection cooling schemes used in desktop computers are not generally applicable to portable computers because of space and battery power constraints.
The present invention relates to laminar jet cooling of heat producing components in an apparatus such as a portable computer. A low velocity, laminar jet of air is directly impinged on the surface of a heat producing component such as a microprocessor chip. A laminar jet flow has a very low mass flow rate and has a high convection heat transfer rate at the stagnation region of the flow. An air driving device such as a small energy efficient fan, an acoustic resonance device, or a small electromagnetically driven actuator assembly can be used to provide laminar jet air flow on the heat producing component. For any apparatus that places a premium on conserving power, delivering laminar jet air flow provides a way to dissipate heat while only minimally draining the power source of the apparatus.
In one embodiment of the invention, an apparatus for cooling heated bodies includes a heat producing component and an air driving device such as a fan, an acoustic resonance device or an electromagnetically driven actuator assembly, which produces a laminar jet of air having a Reynolds number below 2000, to cool the heat producing component. The laminar air flow preferably has a Reynolds number between 1500 and 60 and more preferably between 1500 and 500. The heat producing component can be a microprocessor.
The apparatus further includes a directing device such as a tubing for impinging the laminar air from the air driving device directly on the heat producing component.
In another embodiment of the invention, a laminar jet air cooling device includes a fan, an acoustic resonance device, or an electromagnetically driven actuator device for impinging a laminar jet of air directly on a heat producing electronic component mounted on a circuit board and a tubing coupled to the air driving device and having an outlet above the heat producing electronic component. The outlet directs the laminar jet of air on the heat producing electronic component at a predetermined angle, 90 degrees or less. The laminar air flow has a Reynolds number below 2000, preferably between about 1500 and 60, and more preferably between about 1500 and 500.
In another embodiment of the laminar jet air cooling device, the tubing bifurcates over and below the circuit board such that the tubing over the circuit board directs the laminar jet of air over the heat producing electronic component and the tubing under the circuit board forces the air away from the circuit board to dissipate additional heat.
The laminar jet air cooling device can further include a heat pipe mounted on the underside of the circuit board and connected to a keyboard of a portable system containing the circuit board for transferring heat from the circuit board to the keyboard.
In another embodiment of the invention, a portable computer system includes a circuit board containing a heat producing electronic component such as a microprocessor, and an air driving device such as a fan, an acoustic resonance device, or an electromagnetically driven actuator device for impinging a laminar jet of air directly on the heat producing electronic component.
The portable computer further has a tubing coupled to the air driving device and an outlet above the heat producing electronic component. The outlet directs the laminar jet of air on a surface of the heat producing electronic component at a predetermined angle, 90 degrees or less, over the heat producing electronic component.
In another embodiment of the portable computer system, a tubing bifurcates over and below the circuit board such that the tubing over the circuit board directs the laminar jet of air over the heat producing electronic component and the tubing under the circuit board forces the air out through a vent located close to the heat producing electronic component.
The portable computer system can further have a heat pipe mounted on the underside of the circuit board and connected to a keyboard for transferring heat from the circuit board to the keyboard.
The portable computer system can also have a card and a power supply positioned above the circuit board such that flowing air from the laminar jet of air carries heat away from the card and the power supply through the outlet vent.
In still another embodiment of the invention, a method of cooling a portable computer includes delivering a laminar jet of air to a heat producing electronic component mounted on a circuit board disposed within a portable computer. The laminar jet of air is directed over the heat producing electronic component at a predetermined angle over the heat producing electronic component.
A laminar jet of air can be directed on the heat producing electronic component from over the circuit board and also under the circuit board for letting the air escape through a vent disposed in the wall of the portable computer.